Credit

Caption

Rust fungus. Coloured scanning electron micrograph (SEM) of reproductive cells (spores, red) clinging to a fruiting body (reproductive structure) of the rust fungus Gymnosporangium sabinae. The fungal growth has occurred on a pear tree leaf. Rusts are parasitic fungi that cause some of the most destructive plant diseases. The disease appears as numerous rusty, orange spots that rupture the epidermal layers of the leaves. The fungus rarely causes the tree to die but it greatly reduces its ability to photosynthesize (produce food from sunlight), often leading to severely reduced yields. Magnification: x210 when printed 10 centimetres wide.